Please help!!!

When I try to backup computer using Backup and Restore, I get the message
that "Windows cannot find backup devices on your computer. The requested
system device cannot be found." However, I can see my backup drive in
Internet Explorer, can open it, and can copy files to it. I also can back up
files to it using the Backup and Restore.

Why does my computer find my backup drive (external USB) when I try to back
up files only using Backup and Restore, but cannot find the Drive if I use
Backup up Computer in Backup and Restore?

Please help!